Smoke Domain and Divisions
Smoke Domain and Smoke Flow Objects have to be different objects. An object cannot be Domain and Flow.

To change the settings for Flow, select the flow object and then modify the flow settings.

From the Blender Manual:


  At least a Domain object and one Flow object are required to create a smoke simulation. 
  
  A basic workflow looks like this:
  
  Create a Domain object that defines the bounds of the simulation volume.
  
  Define a Flow object or objects which will emit smoke and fire.
  
  Set Collision objects to make the smoke interact with objects in the scene.
  
  Assign a Volumetric material to the domain object.
  
  Save the blend-file.
  
  Bake the simulation.